


Unanticipated Change of Plans

by ozuttly



Category: Kamen Rider Ex-Aid
Genre: Alternate Universe, Interspecies Relationship, Interspecies Sex, M/M, Merpeople, Non-Human Genitalia, spitroasing
Language: English
Status: Completed
Published: 2019-03-06
Updated: 2019-04-01
Packaged: 2019-11-12 19:26:30
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 14,987
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18016934
Author URL: https://archiveofourown.org/users/ozuttly/pseuds/ozuttly
Summary: Hiiro makes a mistake and ends up being transferred from his surgical position at Seito University Hospital to the medical staff of Genm Corp's oceanic research facility on a tiny uninhabited island in the middle of the ocean. The position is temporary - only a year - but it isn't long into his stay that he realizes this place, and its medical staff, are not exactly what he's used to.Especially when it comes to Kujou Kiriya and Houjou Emu.





	1. Chapter 1

Hiiro doesn’t like change. 

He hasn’t liked it since he was a child, has always preferred to have a straight, unchanging path to follow. Get the best grades in school, go to university to become a doctor, become a top ranked surgeon, all straightforward things that he’s already accomplished. Next on the list were to get married, have children and inherit the position of hospital director from his father. His plans for those things fall apart when Saki dies. 

A lot of things fall apart when Saki dies. 

Change comes three months after the event, when he’s still grieving and distracted. He does the one thing that he’s never tolerated ever in his life – he makes a mistake. 

The mistake is minor. The surgery is still successful and the patient lives, but Hiiro feels the crushing weight of knowing that he could have killed someone, much like the doctor who let Saki die on the operating table. He doesn’t tell anyone. 

His father finds out anyways, as Hiiro had expected he would. He takes him out for dinner, and then to that nice new cake shop that just opened up. Hiiro acts as though everything is normal through most of the evening, up until they’re finishing dessert and his father sets down his fork, looking him in the eyes. 

“I think, Hiiro,” he begins, slow and quiet, like he’s not quite sure how to broach the subject. “That you should take a break.” 

Hiiro had been expecting it, but the words still echo in his head as he swallows the piece of strawberry shortcake in his mouth. It feels much drier than it had only moments before. 

“I don’t need a break,” he insists, but Haima is giving him a sad look, as though he pities him. Hiiro knows then that this isn’t just a suggestion. 

“Look, Hiiro, it’s only temporary,” Haima says, the corners of his mouth trying and failing to pull up into an encouraging smile. Hiiro sets his own fork down. 

“What do you mean?” He asks, even though what he wants to ask is ‘what did you do?’. He doesn’t, though, because while his father may be lacking in many ways, he has tried his best to be supportive over the past few months. Hiiro is the one who screwed up, who is likely to keep screwing up. It isn’t Haima’s fault that he needs to think of the patients first.

At the very least, his father looks a little cowed by the question. He takes a deep breath to prepare himself.

“Genm corporation contacted me,” he begins, and Hiiro’s face immediately goes sour. He’s met Dan Kuroto once at a party, and he did not like the man. Luckily they run in different circles, since Genm deals primarily in wildlife conservation and research, not medicine, and he hasn’t had to deal with him again. His father at least notices his distaste, and he awkwardly reaches for his coffee. “It’s not what you’re thinking, I promise. Dan-san isn’t involved personally at all! It’s just that they have this new facility, and they’re looking for a head for their medical staff.”

Hiiro doesn’t like where this is going. 

“I don’t need to be transferred to a lower-stress job,” he says sharply, and his father’s face hardens just a little at his tone before quickly softening again. 

“Hiiro, like I said, it’s temporary,” he insists. Hiiro crosses his arms over his chest like he did when he was a teenager, but at least he doesn’t interrupt. “You’ll be in charge of two other doctors and four nurses. The facility only has 150 people total, so it’ll be a lot slower than the university hospital, but I think a change of pace could be nice.” 

Haima smiles, but Hiiro doesn’t smile back.

“Why does a facility so small need a private medical team?” He asks instead, and his father’s face falls a little bit, as though he had been purposely avoiding that part. 

“It’s because of the remote location. The facility is located on a small uninhabited island--”

“You want me to leave Tokyo?” Hiiro asks, his voice slightly louder than he intended, and his father winces.

“For one year only,” Haima says, and Hiiro can’t help himself, his mouth hangs open a little bit. 

“A year?!” 

“Hiiro,” Haima interrupts before the outrage can get any louder. A waitress is watching their table curiously, and Hiiro realizes that he’s been making a bit of a scene. He quickly turns back to his half-finished cake. “I’m not asking you about this. I’m giving you instructions as your boss.” 

Hiiro’s mouth twists unpleasantly, but he nods his head regardless. He’s never been particularly good at defying his father’s expectations. 

*** 

A month later, he arrives on the island. It’s a small thing in the middle of the ocean, around 50 square kilometers in size – absolutely tiny compared to Tokyo. Hiiro has travelled before, of course, in and outside of Japan, but it’s always been to cities and other bustling centres. This place, in comparison, is abnormally quiet. It will take some getting used to. 

“So, here on the island our focus is to research the local aquatic life,” his guide, Asuna, says as they get off the ferry. She’s a smart and polite woman, and seems like she takes her job seriously. Hiiro has decided that he likes her on that principle alone. “Of course, your job is only to oversee the medical staff. Mostly you’ll deal with routine illnesses, colds, minor injuries, that sort of thing; Houjo-sensei and Kujou-sensei will report directly to you, and will probably be able to explain things to you in more detail...”

She pauses to look down at the clipboard in her hand, then leads him into the main building near the port, introducing him to various staff members that he’s absolutely certain he’s not going to remember the names of. He nods his head politely to them anyways, and tries to instead focus on memorizing the winding path she’s taking through the massive building until they end up in a residential section. 

“Your luggage has already been sent to your room; you’ll be sharing your apartment with Kujou-sensei, and he’s already been informed about your arrival. You have separate bedrooms, of course, but you’ll share a bathroom and living area. All meals are usually taken in the cafeteria. I’ll show you how to get there after you have a chance to settle in,” Asuna says as she stops in front of a rather nondescript door and knocks.

Hiiro isn’t quite sure how he feels about having a roommate. Even in university he had his own private lodgings, and he considers bringing it up, but he doesn’t want to give away how spoiled his upbringing really was. He’s sure that there are already going to be rumours about his arrival – one of the most talented young surgeons in the world giving up his job at Seito University Hospital to come out to an island in the middle of the ocean for a position that wasn’t even his specialty. 

He’s startled out of his thoughts when the door opens, and he comes face to face with a young man who looks hardly old enough to have just finished medical school. He’s dressed casually, wearing a bright pink tank top and a pair of shorts, and Hiiro fights to remain stone-faced in front of his fashion choices. 

Asuna, on the other hand, does not have the same reaction. Instead her entire countenance brightens, and she seems like a different person as she waves excitedly at the man before her. 

“Emu! I wasn’t expecting to see you here!” She exclaims, and then turns back to Hiiro and clears her throat, acting as though her cheerful outburst never happened. “Kagami-sensei, this is Houjou Emu, one of the two resident doctors you’ll be in charge of--” 

She breaks off her sentence as another man appears in the doorway, one arm winding casually around Emu’s shoulders. His outfit isn’t much more professional either – he’s wearing a Hawaiian shirt of all things, and a pair of ripped jeans that makes Hiiro scrunch up his nose in distaste.

“Yo, Poppy,” he says with a little wave before turning his attention to Hiiro. His smile is sharp as he takes in the look of him, still wearing a suit even in the tropical heat, and Hiiro meets his gaze head on with a challenge. 

“Ah, Kiriya! Hiiro, this is Kujou Kiriya, our other doctor! Kiriya, this is Kagami Hiiro, our new head of the medical department!” Asuna says, and she does sound more personable and bubbly now, as though the strange nickname has caused a switch in her personality. 

Hiiro is unaffected. Instead he takes in the look of both Emu and Kiriya and his mouth turns downwards. 

“Which one of you is the on-call doctor at the moment?” He asks, and Asuna’s face falters slightly as Emu perks up. 

“Oh, uh, that’s me! I have my pager, uhm...” He pats down his pockets as Kiriya levels Hiiro with a calculating stare. Hiiro meets it back as Emu turns back to him with a slightly nervous apologetic look. “Uh, back in my room,” he admits. Hiiro is unimpressed. 

“Go get it, then,” he says, his tone stern, and Emu flinches back a little. “All on-call staff are to have their pagers on them at all times, regardless of what you’re doing. We have a very small staff; as one of only three doctors available, you need to be ready to respond to an emergency call at all times.”

“Kagami-sensei, it really isn’t that big of a deal; we only have 150 people here, the chances of an emergency happening so suddenly are--” Asuna begins, but Hiiro cuts her off with a harsh glare. 

“The chances may be low, but not impossible. An on-call doctor not having his pager on him and using his time to goof around is amateurish and not something I’ll stand for as the head doctor,” he says sharply, and Kiriya whistles. 

“You’re a bit of a hardass, aren’t you, Kagami?” He asks, one eyebrow raised, and the smile on his face is far from friendly. That’s fine, though; Hiiro didn’t come here to make friends. 

“I am in charge of running the medical facilities on this island, and I intend to make sure that they are run efficiently. Houjou, go get your pager. Now.” 

Emu flinches, but nods his head and scurries down the hall to his own room. Hiiro has a feeling that even once he gets his pager, he won’t be back.

Asuna clears her throat awkwardly, tapping one finger against her clipboard when Hiiro looks up at her. She seems a bit cowed now, not quite as professional and efficient as she was before. That’s fine, too. Hiiro doesn’t mind being feared by the staff. 

“W-well then, Kagami-sensei. I’ll be back in a few hours to show you to the cafeteria for dinner,” she says, sounding like she wants to do nothing less. 

“It’s fine, I’ll show him where everything is,” Kiriya cuts in, and Hiiro’s gaze goes back to him, hardening into a challenge again when Kiriya shows him a shark-like grin. He may not be particularly skilled when it comes to human relations, but Hiiro knows well enough when somebody is sizing him up as a potential obstacle, and he doesn’t intend to be an easy one to scale. 

He may not have come here on his own terms, but his father gave him a job to do, and he plans to do it to the best of his abilities, whether his staff like him or not. 

*** 

The first two months, surprisingly, go smoothly after the initial bump of introductions are done and over with. 

Kiriya keeps to himself in their suite, only coming out of his room when Emu comes over to play video games or watch movies or whatever the two of them do together. Hiiro, in return, keeps to himself as well, retreating to his room when Emu shows up to give them privacy. He doesn’t know what the relationship between the two of them is, and he doesn’t really care, either. 

Running the medical department at the research facility is a relatively straightforward job, too. It requires a lot more paperwork than he’s used to, but he does it without complaint. Despite his misgivings on the first day, Kiriya and Emu are not bad doctors, and he finds them both easy to work with. Kiriya, he suspects, still doesn’t necessarily like him, but Emu at least is making an effort to be friendly, and it’s been so long since somebody has been genuinely nice to him with no strings attached that Hiiro can’t help but start to like him. 

He still pushes him hard, of course, because he demands excellence in any job, whether it’s from himself or his subordinates, but he finds himself feeling a bit softer, offering an occasional word of praise here and there that always seems to surprise Emu every time he hears it. 

Kiriya, on the other hand, does not seem to want or need his praise. He always has a friendly demeanor, but he holds Hiiro at a clear distance, so Hiiro responds in turn. Their relationship is strictly professional, and Hiiro is fine with that. 

Or, at least, he is fine with that, until he finds out that Kiriya is breaking the rules. 

Staff are to remain inside after an eleven pm curfew. The island is, after all, uninhabited. The risk of injury outside of the facility late at night is high, and Hiiro does not want to deal with accidental deaths on his watch, so he makes sure to instruct security to enforce the curfew strictly. 

Two months after he arrives, he finds out that Kiriya is breaking it. 

It’s a coincidence, really, that he even realizes it. He’s going to the bathroom at midnight when he notices that Kiriya’s door is open, just a smidge. It’s unusual enough in and of itself, and he can’t help but be curious as he glances into the room to see that the bed is empty, and Kiriya is nowhere in sight. 

Hiiro’s face immediately sours. He had expected that, personal dislike aside, Kiriya would at least follow the public safety rules that he had put into place. Finding out that he isn’t immediately puts Hiiro on edge, and before he can even think about it he’s down the hall to Emu’s room, knocking on the door softly so as not to disturb the other staff.

Emu doesn’t answer the door. 

Hiiro’s eyes narrow, and he knocks again, but still, nothing. Emu doesn’t have a roommate, so Hiiro knows that something is up. Some kind of lover’s tryst, maybe? Outside, on the beach, at night. It’s dangerous, and Hiiro has half a mind to report them to security. 

He doesn’t, though, because he doesn’t actually want to humiliate Emu. But he just as well can’t let this slide, so he heads back into his room, grabbing his first aid kit just in case, and then heads down, slipping past the security guard out into the night. 

Most of the island is beach, luckily. There’s a forest in the centre, but Hiiro is not foolish enough to traipse around there at night without a guide. He doubts that Kiriya and Emu are either, and instead focuses on searching the beach near the facility. 

The perimeter of the island is over 30 kilometers, so he knows he has no chance of searching it by himself, but he’s still reluctant to inform security. He decides that if he doesn’t find them after a quick search, he’ll go back in and let them know, but for now he’s determined to save Emu the embarrassment. 

The island is an odd shape, with lots of curves and twists in the beach. Hiiro is only walking for about ten minutes when he can no longer see the shape of the facility in the background, and he’s starting to regret his decision when he notices a different shape on the beach in front of him. 

It’s a person. 

He curses and starts to run, hoping in his heart that it’s not Emu, and then feeling slightly bad about that a moment later when he realizes that it’s Kiriya, his head whipping up to face Hiiro the second he hears his approaching footsteps. The instant he recognizes him, he starts to struggle, trying to push himself into the water, and Hiiro has no idea why until he realizes that Kiriya does not currently have any legs. 

He stops immediately, taking in the yellow, eel-like tail that extends down from Kiriya’s pelvis, and Kiriya actually hisses at him like an animal, warning him not to come closer. 

Perhaps, ordinarily, Hiiro would have listened, but he can see from here that there’s blood on the sand, and the doctor in him immediately overrides the confusion that’s threatening to take him over. 

“Kujou,” he says, his voice a bit softer than he intends, and Kiriya digs his hands into the sand, trying to push himself into the water again. He’s too far up on the beach, though, and his tail is too long and ungainly in the sand. Hiiro is fascinated by it as he steps in closer, seeing what looks like a bite mark of some kind standing out against the otherwise smooth skin. 

“Fuck off Kagami,” Kiriya hisses at him, and it snaps Hiiro back into the here and now, because he just glares at him in response, crouching down next to him with his first aid kid. 

“Let me look at that bite,” Hiiro demands, and Kiriya growls at him, low and deep in his chest. It’s incredibly threatening, and Hiiro’s heartbeat speeds up just a bit at hearing it. 

“Get out of here and go back to bed,” Kiriya snaps. “Think of this as a dream and we can go back to working together without any problem.” 

Hiiro frowns, especially when Kiriya jerks away from his fingers as he tries to get a better look at the bite. He flashes wickedly sharp teeth then, far sharper than any human’s teeth had any right being, and Hiiro swallows heavily before he ignores the warning and reaches forward again. 

“If you touch me, I’m going to bite you,” Kiriya warns, his voice deadly serious, but he doesn’t flinch away again as Hiiro leans in closer. 

“Look, Kujou,” Hiiro says, his own voice as calm as he can make it. “I don’t care what you are or what’s going on. You’re injured, and it looks like you’ll need sutures before you bleed out all over the sand. I’m a doctor, and I’m going to help you, whether you like it or not. Do you understand?”

Kiriya looks surprised, and then that surprise fades into suspicion. He looks like he doesn’t quite believe what Hiiro said, but he doesn’t flash his teeth this time when Hiiro leans in to touch his tail. 

It feels almost slimy to the touch, which Hiiro isn’t expecting, but he gets a good look at the wound before pulling off his shirt – an old t-shirt from university that he only ever wore to sleep in – and pressing it to the flesh to staunch the bleeding. 

Kiriya hisses, but lets him do his job as he reaches for his first aid kit and opens it up. 

“Where’s Emu?” he asks as he cleans the wounds, which are luckily no longer bleeding as profusely. Kiriya eyes him warily, and Hiiro pulls out his suture kit. “I knocked on his door when I realized that you were missing, and he wasn’t there. Obviously the two of you were...” He trails off, unable to say what he’s thinking, and Kiriya snorts at him. 

“He went to sneak back in and get a first aid kit,” he says, and Hiiro relaxes a little, glad to know that Emu, at least, didn’t seem to be hurt.

“This would be better to take care of in a sterile environment,” Hiiro warns, and Kiriya hisses at him again. He rolls his eyes, not finding it nearly as threatening anymore. “Relax, I’m not taking you back to the facility like this. Unless you can...” He pauses and waves one hand, towards his own legs, unsure exactly of how Kiriya manages to look the way he does during the day if this is his natural form. Hiiro’s assuming it is. 

“Not when I’m hurt,” Kiriya grinds out, but he seems to relax a little bit once more when Hiiro says that he’s not going to turn him in. “I’ll be able to in a few hours, but... Look, there’s a cave a little ways down the beach, I can hang out there. I’ll be back before sunrise, and we can pretend this never happened.” 

Hiiro narrows his eyes at him as he finishes stitching the wounds shut, and he puts the suture kit back into his first aid kit. 

“You can’t swim in the state that you’re in,” he says sharply. “And if you try to drag yourself down the beach, you’ll tear out your sutures.” 

Kiriya glares at him, and makes an irritated clicking sound in the back of his throat. 

“So I’ll wait for Emu to get back, Kagami. Look, I appreciate the help, but I don’t want you here. I can handle myself perfectly fine on my own,” he says, his voice cold enough that Hiiro actually shivers. He recovers rather quickly, though, and glares right back at Kiriya, not giving him an inch. 

“Right now, you’re my patient, as well as my subordinate. I’m not going to leave you here to injure yourself unnecessarily,” he shoots back, and Kiriya actually looks a little bit surprised. It passes quickly enough, but at least he doesn’t seem as defensive as he did earlier, and Hiiro takes a deep breath as he considers their options. He can’t carry Kiriya down the beach; his tail is at least twelve feet long without even taking into account his human half, and dragging him will reopen his wounds. 

He’s still thinking about what to do when he notices Kiriya’s eyes focusing on something behind him, before they widen in alarm. 

“Wait, Emu--!” He begins, and Hiiro tries to turn around before all of a sudden something strikes him in the back of the head, and everything goes dark.


	2. Chapter 2

Hiiro wakes up slowly. 

His head feels sore and fuzzy, and there’s a slow, pounding ache right at the base of his skull. For a moment he doesn’t know why as he tries to piece together exactly where he is and what happened. He’s vaguely aware of hands on his face, somebody pulling his eyes open and shining a penlight into his pupils. 

“Is he ok?” he hears a voice ask, though it sounds distant and he can’t quite seem to focus on it. 

“It doesn’t look like you concussed him, at least,” another voice answers back, and it sounds so familiar... 

He remembers a long, yellow tail and blood in the sand. 

Slowly, he manages to pull his eyes open of his own accord, and sees that Kiriya’s face is hovering very near to his own. He doesn’t know why at first, but he starts to remember when he catches sight of the other man’s all-too-sharp teeth that are even more worrying when they’re this close to his person. 

He’s too tired and his head hurts too much to actually react accordingly to that, though, and instead he just swats grumpily at the flashlight shining into his face. Or he tries to, but finds that he can’t actually move his hands from his sides for some reason, and he mutters something under his breath as he wiggles ineffectually instead.

“Hiiro-san? Are you ok?” It’s the first voice again, and now that he’s starting to regain his senses Hiiro can tell that it’s Emu’s. He sounds worried.

Hiiro slowly cracks his eyes open again – when had he even closed them? - and the fuzzy world around him comes better into focus. 

He’s in a cave of some kind, though it’s not completely enclosed. Moonlight shines in from both the entrance and a hole up above, illuminating the surroundings with the help of what looks to be a waterproof utility lamp. There’s a pool of water less than a foot away from his feet, and he notices with disdain that Kiriya’s tail is almost entirely submerged. 

“You’re going to get your sutures infected,” he mumbles, and Kiriya blinks before he cracks a smile at him. It isn’t even his usual empty, slightly mocking smile. 

“I’m fine. Waterproof bandage,” he says, and then turns back to look over his shoulder at Emu, who is standing by the edge of the natural pool and fidgeting nervously. “He’s alright, Emu don’t worry.” 

Hiiro squints at him, because he would much prefer that Kiriya stay out of the water, but then on second thought, he isn’t really sure if he can. Hiiro may be an expert on the human body, but he’s not nearly as well versed in supposedly-mythological creatures.

It’s while he’s considering this that he tries to move his hands again, and frowns when once again, they won’t obey him. This time he has the wherewithal to look down at his arms, and realizes with a start that the reason he can’t move is that he’s tied up. 

“We’re really sorry, Hiiro-san,” Emu says, and Hiiro glares at him. He at least looks sufficiently sorry, while Kiriya only looks vaguely amused by his reaction. 

“If you’re sorry, why did you tie me up?” He asks, then frowns. “Moreover, how did we get here? Surely you didn’t carry both of us.” 

Emu looks a little bashful as the scratches the side of his cheek, and Hiiro’s eyebrows shoot up. No way. He and Kiriya together must have weighed over 400 pounds, there’s no way that Emu could possibly--

“He’s stronger than he looks,” Kiriya says with a little shrug, clearly not at all bothered by this. “And we tied you up because honestly, Kagami, we don’t trust you.” 

Emu looks apologetic, but Hiiro hardly has it in him to care at the moment. He had always trusted him to be the gentler of the two doctors under his command, and now...

“You hit me over the head,” he says accusingly, and Emu flinches. 

“I panicked,” he admits, and Hiiro scowls at him. Kiriya doesn’t seem to appreciate the look, though, and he reaches over and pinches Hiiro’s shoulder. Hiiro squeaks, then very quickly shuts his mouth and pretends that he didn’t. Emu seems to relax a bit. “I’m sorry, really. I didn’t even know it was you, Hiiro-san – I thought maybe one of the guards...” 

He trails off, and Hiiro slowly nods his head, even though the action makes his vision go a little fuzzy and the dull ache that’s been pounding in the back of his skull compound by ten times. He can’t even press his hands to his temples considering the ropes, and he has to try very hard to restrain his groan. Emu tenses right back up again, and he comes in close beside Kiriya, gently feeling at the bump on the back of Hiiro’s head. Luckily his head doesn’t feel wet, and Emu’s fingers don’t come away red, so it probably isn’t actually as bad as it feels, but that doesn’t stop it from feeling terrible. 

“Maybe I should take you to the infirmary,” Emu worries, and Hiiro glances over at Kiriya, noting the way that he stiffens ever so slightly at the suggestion. Hiiro suspects that he won’t actually argue if it’s what Emu decides to do, but it’s clear that he also doesn’t like the idea. Hiiro isn’t sure why he cares what Kiriya thinks, but he does. 

“No, I’m fine. If we go to the infirmary at this hour, we’ll have to explain what we were doing out past curfew. Also Kujou can’t go back like this,” he says, and Kiriya once again looks like he’s a bit surprised by what Hiiro’s saying, like he can’t actually believe that he’s being agreeable. Emu looks the same, and Hiiro feels a little annoyed that they apparently think so little of him. 

“You’re not going to turn us in?” Emu asks, slowly, and Hiiro sighs slowly. He had expected the question, but it still irritates him. 

“Of course not. Security wouldn’t believe this story anyways,” he says, and a small, relieved smile breaks out on Emu’s face. Hiiro blames the way it makes his heart speed up a little bit on the head injury. “That being said, I am still angry at you both. Things could have ended up far worse, and if you hadn’t broken curfew--” 

“We can’t stay locked up in there all the time the way you can,” Kiriya cuts him off, and he smirks a little at the way Hiiro scrunches up his nose at him. 

“We need to swim at least once a week,” Emu explains, seeming much more comfortable now that Hiiro has professed he has no intention to tell on them. He even pulls out a pocket knife and begins to cut the rope keeping Hiiro tied up. Kiriya gives him a wary look, but he doesn’t actually protest – instead he just slinks back into the water a bit, clearly not comfortable being as close to Hiiro when he can use his hands. 

It annoys Hiiro a little bit, for reasons that he can’t actually name, but he latches onto something else that requires more immediate attention. 

“’We’?” He asks, looking at Emu with slightly raised eyebrows. “You’re....” He trails off, waving a hand at Kiriya’s general tail section. “...The same?”

Emu hesitates for a moment as he finishes cutting Hiiro’s bonds – Hiiro wonders where they even got the rope – and Hiiro gives him time to answer. He realizes belatedly that Emu might not have actually meant to give that information away, and he’s about to say that he doesn’t have to answer when he does. 

“We’re, uh, different subspecies, but. Yeah,” Emu says, licking his lips as though his mouth has gone dry. 

It makes Hiiro curious, more than anything. He wonders what Emu looks like, when he’s not pretending to be human. He knows that it would be deeply inappropriate to ask, so he keeps his thoughts private, but he still wonders. 

Kiriya clears his throat, and Hiiro snaps out of his thoughts. He looks down at his hands, now free, and slowly rotates his wrists to make sure that he has his full range of movement. Kiriya and Emu watch him, warily, and he grits his teeth a little at their obvious distrust. 

“I’m not going to tell anybody,” he says, even though he feels it should have been obvious. Nobody would possibly believe him anyways, and he actually does care about the well being of the staff under his control. Normally he doesn’t care what people think of him, and he’s exceptionally skilled at letting the opinions of people who don’t matter roll off his back, but this is really bugging him. He doesn’t know or want to examine why, though. “You can keep an eye on me if you want to – hell, you live with me. I highly doubt that I can sneak away to tell somebody without one of you noticing.”

Emu softens a little, at his profession, though he still looks a little wary. Kiriya is just watching him, considering, and he meets his gaze like a challenge. Rather than looking away, Kiriya’s mouth twitches a bit at the corners, and whatever he sees must have pleased him.

“Ok, fine. You’re going to be under our surveillance then, Kagami,” He says, his voice as chipper as anything, and he relaxes a little into the water, smiling like a pleased cat. The expression is a little unsettling. “And if you do tell anyone, know that I will eat you, got it?” 

Hiiro highly doubts that it’s an empty threat. One look at Kiriya’s teeth tells him that had his name and position not been so important, the negotiations would not have even gotten to this point to begin with. The merman holds out one hand for Hiiro to shake, and it’s undoubtedly another challenge. 

“Kiriya-san,” Emu chides, sounding a bit horrified, but Hiiro just levels Kiriya’s gaze to show that while he may be a bit scary, he’s not actually afraid of him. 

“Deal,” he says sharply, and shakes Kiriya’s hand. 

He isn’t actually expecting Kiriya to pull him into the water. 

He lets out a startled yelp, because he took swimming lessons back in elementary school, but he hasn’t actually used them since then. He clings to Kiriya’s shoulders tightly while Emu squawks in surprise, and Kiriya laughs at him. 

“Can’t swim, Kagami?” He asks, and Hiiro feels something long and smooth sliding around his legs. The feeling makes his heart jump in his chest, and for a moment he thinks that Kiriya might drag him under and make good on his threat to eat him. But then the thing sliding against his legs changes, and he can’t actually see from the low light and how murky the water is, but he can feel a heat near him, and then there’s another set of legs brushing against his own. 

“Kiriya-san, that’s mean!” Emu exclaims from the edge of the pool as he grabs Hiiro’s upper arm and pulls him back to the edge. Kiriya just grins, looking entirely too pleased with himself. He pulls himself up and out of the water the same time that Emu hauls Hiiro up, and winces just a little bit as his wound – now on his thigh – brushes against the stone. 

Hiiro has half a mind to lecture him about keeping it clean, but he’s a bit too shaken to really say anything. 

Distantly, as Emu offers Kiriya his coat so that he isn’t completely naked, Hiiro wonders exactly what he managed to get himself dragged into.


	3. Chapter 3

Sneaking back into the building before dawn (Hiiro was apparently out for a while) is easier said than done, but somehow they manage to do it (after locating Kiriya’s clothes stashed at the back of the cave). Emu slides back into his room to get a few hours of sleep before the start of his morning shift, and Hiiro and Kiriya return to their apartment as well. 

Hiiro is still processing things, but Kiriya seems calm as he decides to forego sleep in favour of making breakfast. Hiiro can’t quite sleep himself, what with the pounding in his head, so he sits down at the kitchen table with some wayward paperwork that needs to be completed and listens to the sounds of Kiriya puttering about the kitchen. 

He manages to re-read the same sentence about five times before a plate of scrambled eggs is placed right on top of his papers, and he scowls a little as he looks up to see Kiriya calmly pulling out the seat across the table from him. 

“Eat, it’ll help you feel better,” he says, and Hiiro wants to disagree with him, but he hasn’t eaten anything since dinner the day before, and his stomach isn’t quite as stubborn as he is. When it makes a low, embarrassing growl, he reluctantly picks up his fork and digs in, making a pleased noise when he realizes that the food is actually pretty good. Kiriya leans back and preens a little. “Yeah I’m a good cook, I know.” 

Hiiro doesn’t even want to dignify that with a response, so instead he focuses on breakfast. And, to his chagrin, he does feel better when he’s done, even though his head is still killing him. 

“You seem more relaxed now,” he says to Kiriya as the other man takes his plate away and retreats to the sink to wash their dishes. “You didn’t even threaten me.” 

Kiriya rolls his eyes and snorts through his nose. 

“Hey, I’ll have you know I’m a pretty agreeable guy, most of the time,” he says, and Hiiro stares at him blankly. 

“You said you would eat me,” he points out, and Kiriya just shrugs. 

“Only if you put us in danger,” he replies casually, then peers back at Hiiro with a look on his face that the surgeon just can’t quite seem to read. “But I don’t think you will. I think you’re a jerk, Kagami, but I don’t think you’re necessarily a bad guy. Besides, I don’t think you’d do that to Emu.” 

Hiiro chokes a little bit on air at that, and Kiriya seems to smile knowingly as he hands him a glass of water. Hiiro glares at him as he swallows it down.

“I don’t know what you mean by that,” he says, because it’s not like he’s particularly close to Emu. He thinks he has potential as a doctor, despite their rough start, and he wants him to utilize that, yes, and yeah, maybe he kind of likes his kindness and his enthusiasm, and... Maybe he thinks he’s a little bit cute when he smiles. Hiiro’s cheeks flush a little, and he takes another swallow of water. That doesn’t matter, anyways, because Emu and Kiriya are clearly together, and Hiiro has no intention of getting between them, especially so soon after losing his fiancee. 

Kiriya watches him silently, cataloguing his reactions, before he mercifully shrugs his shoulders. 

“Maybe I’m wrong,” he says without actually specifying what he might be wrong about. Hiiro wants to agree with him, to insist that yes, he is wrong, but he also doesn’t want to appear too invested in this, so he takes another sip of his water instead, trying to will the colour away from his cheeks. Kiriya seems to take pity on him and changes the subject. “Anyways, what do you have to do today? Emu and I can take care of it and you can take the day off. You might not be concussed, but he hit you pretty hard.”

Hiiro frowns, immediately balking at the idea of pushing his responsibilities onto somebody else. 

“I’m fine,” he insists, but Kiriya just levels him with a Look until he shifts uncomfortably in his chair and caves in. “It’s just paperwork, mostly, and setting the nurse’s schedules for the week. I can do most of it tomorrow, I suppose...” 

“I’ll set up the nurse schedule and then run it by you, how’s that sound?” Kiriya suggests, and Hiiro slowly nods. As much as he hates to admit it, he’s starting to feel tired, and taking a day off to rest is starting to seem more and more like a good idea. Kiriya must notice, because he smiles in that smug, pleased way that means he’s won. 

*** 

Taking a day off was more boring than it sounded, and by the time Kiriya and Emu returned to the apartment after their shift Hiiro felt like he was ready to crawl out of his skin in search of something to do. 

“You know,” Kiriya says as he flops down on the couch. “You didn’t need to text us every hour.”

Hiiro fights the slight flush coming up to his cheeks, and Emu looks amused as he sits down next to Kiriya on the couch, snuggling up next to him while Kiriya wraps an arm around his shoulders. Hiiro briefly thinks that they’re showing off unnecessarily, before he reassures himself that he doesn’t care even if they are. 

“I was just making sure you were on task,” He says, and Emu and Kiriya share a look together that Hiiro is sure is at his expense. 

“At least you’re feeling better,” Emu chirps, and the flush that Hiiro had been fighting comes back full force. He can just imagine the look that Kiriya is giving him, so he stubbornly focuses on the table in front of him as though it’s far more entertaining than it actually is. He curses Kiriya for implying things earlier in the day, because now he can’t stop thinking about it. 

“Anyways,” Kiriya says after a few moments of somewhat-awkward silence. “Emu and I are going out tonight, and we wanted you to come with us. You know, so we can talk.” 

Hiiro can feel the frown on his face before he even realizes he’s making it. The idea of sneaking out past a curfew that he set into place does not sit well with him. Not to mention the fact that Kiriya is still injured. 

“I advise against it,” he says, and he tries to ignore the way that Emu’s face falls a little bit. “You’re still healing, and I don’t want to exacerbate your injury,” he adds quickly, and Kiriya makes an annoyed little noise in the back of his throat. 

“It wasn’t that bad,” he insists, but Hiiro meets his gaze head on. 

“You needed ten sutures. Even with a waterproof bandage I don’t want you swimming until the stitches can come out,” he says, and Kiriya groans. Emu looks like he’s torn between who he wants to support, both concerned for Kiriya’s health while also understanding his position. Truth be told Hiiro isn’t sure if Kiriya can wait the ten days until the stitches can come out; he knows entirely too little about their situation. 

“I’ll be fine, Kagami,” Kiriya needles, before switching to a different tactic. “Don’t you have questions?” 

Hiiro bites the inside of his lip, because he does have questions, but he also doesn’t want to be manipulated into making a poor decision for his patient. Luckily, Emu decides to jump in with a compromise. 

“We’ll stay close to the shore tonight,” he says, and gives Hiiro this pleading look that Hiiro never knew he was weak to until that moment. Hiiro hesitates for a few minutes longer, but Emu is looking up at him through his eyelashes, and finally he clears his throat and looks away in defeat. 

“Alright, fine, but I want to take a look at your leg before you...” He waves a hand in the air to somehow indicate what he assumes to be some sort of magical transformation. Kiriya snorts, but he seems more amused than annoyed now, at least. 

“Alright, sounds good. We’ll head out just before midnight.”

*** 

They end up going back to the cave they were in the first night. Apparently Kiriya and Emu had been using it as a place to store their clothes while they swam, as it was just close enough to the facility to be convenient but far enough away that routine patrols wouldn’t find it. 

Once they get there, Hiiro settles down on the ground and beckons Kiriya over so he can get a good look at the sutures. 

They look good, honestly. Better than Hiiro had been expecting, and his surprise must have shown on his face because Kiriya just shrugs nonchalantly. 

“We heal fast,” he says, and Hiiro nods. He applies the spray bandage then, and Kiriya drops his pants completely before tugging off his shirt. Hiiro’s face turns red as he tries very hard not to look at what is in front of him, and Kiriya must have noticed, because there’s a smug little grin on his face as he makes his way down to the water. 

Emu is already naked himself, sliding into the pool with a little sigh. Hiiro is thankful that the water is murky enough that he can’t actually see anything, but he still feels his flush worsen as he gets a good look at Emu’s torso. He’s far more muscular than Hiiro would have ever guessed, with very defined abs and strong arms. The sight does funny things to Hiiro’s stomach, and he’s glad when Emu eases into the water past what he can see. 

Kiriya hums and slides in next to him, and they both disappear beneath the surface.   
They’re under for a few minutes, to the point where Hiiro begins to wonder if they’ve just abandoned him and left, but then Emu resurfaces with a smile on his face and Hiiro finds his breath taken away. 

Kiriya had looked almost completely human from the waist up, besides his teeth, but Emu is completely different. There are delicate fins where his ears should be, and his cheeks are dotted with little pink scales, almost like freckles. A set of gills on his neck close up once they come out of the water, and Hiiro can see that there are scales on his shoulders and back too, in little patches that don’t quite seem to have a pattern. 

He’s very pretty, in a weird and alien way. Hiiro finds that he likes it. 

And then Kiriya comes up, slinging his arm around Emu’s shoulders. 

“You’re staring, Kagami,” he says with a little smirk, and Hiiro quickly turns his eyes away. Emu laughs a little, clearly not bothered, and Hiiro is glad because it means that Kiriya hasn’t told him about his suspicions. 

“It’s a little much to take in, if you’re not used to it,” Emu says, like he’s trying to reassure Hiiro, and Hiiro can’t quite stop his mouth before it blurts out the first thing that comes to mind. 

“No, it’s fine. You look good,” he says, and then mentally kicks himself. Emu blinks owlishly at him, and then smiles, a slight hint of a flush coming to his own cheeks as he preens at the compliment. Kiriya rolls his eyes, then hauls himself up onto the edge of the pool with a little grunt. 

“Ok, we’re all settled in now. Question time. Go ahead and shoot,” he says, making a little finger guns motion to Hiiro, who meets his enthusiasm with a blank stare. Lack of amusement with Kiriya’s antics aside, though, he does have questions to be answered, and the first one is the most important that has been sticking out in his mind all day. 

“Did you two really go to medical school?” he asks, eyes narrowed, and Emu and Kiriya both balk a little bit. They share a look between the two of them, before Emu bites down on his lip to suppress a laugh, and Hiiro can see that his teeth are a little bit sharp too, though nowhere near the daggers that Kiriya has in his mouth. 

“Yes, we went to medical school,” Kiriya says, sounding both entertained and exasperated at the same time. Hiiro thinks that the exasperation is a little uncalled for, because that was a very important question. He had been entrusting these two with peoples’ lives, and he needed to know that they were well trained in human anatomy. Then again, he supposed, he had seen them working over the past two months, and they had been very competent. Perhaps it was a silly question after all. 

“I actually just finished my internship at your old hospital,” Emu adds, and Hiiro’s eyebrows rise a little in surprise. “I was in the pediatric department mostly before going on to become a general physician, so our paths never really crossed, but I’d heard of you. I was a bit surprised when you ended up coming here, of all places.” 

Hiiro can’t help the small frown that comes to his face, and he quickly looks away from Emu’s eyes. It’s a bit embarrassing to reveal exactly why he did come here, and he doesn’t want to lose face in front of his employees. 

“There were personal reasons,” he says instead, and Emu looks like he wants to ask more, but he keeps his mouth shut. 

“I worked there too, you know,” Kiriya pipes in, and Hiiro turns back to him with one eyebrow raised. “Only for a year, in the morgue. Wanted to become a coroner before I went and became a GP. We met once, but it was a while ago. Only in passing. I remember thinking you were a jerk, and then I turned out to be right.” 

Hiiro scowls at him while Emu chastises him for being rude, and Kiriya just laughs, clearly unbothered.

“Relax, relax. I never said I thought you were a bad guy. Just a little uptight, that’s all,” he adds. Hiiro still isn’t entirely amused, but he accepts that there was no malice in Kiriya’s comment. 

“Perhaps you could stand to be a bit more uptight,” he says, and Kiriya grins, clearly pleased by the retaliation. Emu glances between the two of them and then sighs, resting his arms on the edge of the pool. 

“Do you have any other questions, Hiiro-san?” he asks, and Hiiro pauses for a second to think about it. He does, of course, but putting them in order is difficult, and he isn’t sure what’s appropriate and isn’t appropriate to ask. Clearly Emu and Kiriya have lived on the surface world for quite a while, so he suspects that such isn’t exactly unusual among their species. 

“Why are you here?” He asks finally, and gets a set of raised eyebrows in return. “You both used to live in Tokyo. Why come all the way out here?” 

Emu hums a little, and Kiriya runs his fingers over his back in a soothing gesture. It’s rather intimate, but casual, and Hiiro doubts they even realize they’re doing it. 

“Genm corp is... Well, do you actually know what this facility is for, Hiiro-san?” Emu asks, his voice soft, and Hiiro frowns. 

“Asuna told me that it’s for researching the local aquatic life,” Hiiro says, then realizes that that makes him sound particularly uninformed. “Genm contacted my father about filling the position, I’m sure that they talked specifics over with him.” 

It still makes him sound uninformed, but Kiriya and Emu at least seem to have expected that sort of answer. 

“Yeah, well, that’s the official purpose, anyways. What they mean by ‘aquatic life’ is people like us,” Kiriya explains with a languid stretch. He lays down on the ground, most of his tail still in the water. “Emu and I are here to make sure that they don’t find anything out.” 

“Wouldn’t it make more sense to pose as a researcher?” Hiiro asks, and Kiriya snorts. 

“We’re not marine biologists, we’re doctors,” he points out, and yes, that does make sense. Hiiro feels a bit silly for bringing it up now, and Emu just smiles at him from where he’s resting at the edge of the pool. 

“The researchers are place under heavier surveillance anyways,” he explains. “As the medical staff we’re generally expected not to know anything about what’s really going on, so we’re left on our own more. It makes it easier.” 

That makes sense too, and Hiiro nods his head. He has more questions, but he feels like any more would be getting to be invasive, and he feels like secrecy is probably a bit part of who and what Emu and Kiriya are. He doesn’t want to compromise that any more than he already has. 

“That’s all I wanted to know,” he says, and Emu looks surprised, whereas Kiriya is just giving him that calculating, observing look once more. 

“Are you sure? We don’t mind answering more of your questions,” Emu begins, and Hiiro pauses for a second. There is one thing...

“Do drugs affect you the same way? If either of you get sick or injured, I need to know how to treat you despite your anatomy,” he says after a second, and Kiriya chuckles a little. 

“Of course you would ask that,” he says, and Hiiro has half a mind to be offended, but instead of looking condescending Kiriya actually looks a little... fond? Which can’t be right at all. 

“You can treat us just like you would a normal human patient,” Emu says, and Hiiro nods. 

“Then that’s it.” 

“In that case,” Kiriya says as he flops back into the water, splashing Hiiro maybe accidentally on purpose. “Emu and I are going to go for a swim. You can head back now, or--” 

“I’ll stay,” Hiiro says, partially because he doesn’t want to try and sneak back in by himself, and partially because he wants to see if he can get a glimpse of the two of them out in the ocean. 

He realizes he forgot to ask about what caused the bite mark when the two of them disappear into the open ocean.


	4. Chapter 4

Over the next few months, things changed gradually. Emu and Kiriya continued to sneak out at night, usually a few times a week, but now they brought Hiiro with them. Kiriya said that it was because they wanted to keep an eye on him, but after a month or two spending time with Kiriya and Emu, even if it was only to hang out in the cave for a bit before they went out on their nightly swim, became second nature. 

It was four months after Hiiro learned Emu and Kiriya’s secret that things started to really change between them. 

“You seriously can’t tell me that you don’t actually know how to swim,” Kiriya says, stretched out on the floor of the cave and basking in the moonlight shining through the hole in the ceiling. He looks incredibly comfortable, and Hiiro has learned that he likes to be out of the water in this form just as much as he likes to be in it. Hiiro always finds it a little fascinating to see him without the murkiness of the water obstructing his view, and after the first month or so he doesn’t bother to hide his observation anymore. 

“I can swim,” Hiiro says, a little indignant. “I learned in elementary school, I’ve just never needed to.” 

Emu and Kiriya share a look together that clearly says they don’t believe him. 

“You live on an island, Hiiro,” Kiriya shoots back, incredulous. Hiiro wonders when it was that he had started using his first name, and finds he can’t remember. “Even Japan is an island. How have you never swam? Have you never gone to the beach before or what?” 

Hiiro glances at Emu, hoping for some reinforcement, but Emu looks just as curious as Kiriya, and Hiiro sighs as he scratches the back of his neck absently. 

“No, not before coming here,” he admits, and Emu’s jaw drops. 

“Seriously, never? How?” He asks, and Hiiro narrows his eyes at him. He considers not answering for a moment, before he decides that Emu really doesn’t mean any harm, and it wouldn’t do any harm to tell him. 

“In high school I was focused on my grades and cram school. In university I was focused on my grades. After university I was focused on my career. I’ve never had time for pleasure trips or those kinds of outings,” he explains. He closes his eyes and leans back against the rock wall of the cave behind him, then opens his eyes again a moment later when he realizes that all he can hear is silence. 

Emu and Kiriya are both staring at him. He shifts uncomfortably against the wall, before Kiriya lets out a long sigh. 

“Hiiro, that is about the saddest thing I’ve ever heard,” he says, and Emu winces a bit but nods his head in agreement. He soon perks up though as an idea occurs to him. 

“We could just teach you to swim now,” he suggests, and Kiriya makes a little trilling noise in the back of his throat that Hiiro has learned means he’s interested in something. Hiiro immediately frowns and shakes his head, recalling the last time he had ended up ‘swimming’ with Kiriya. 

“No, it’s fine, I don’t need it,” he says quickly, and Emu frowns, pulling his torso out of the water. 

“Come on, it’ll be fun,” he wheedles, and Hiiro quickly finds that his inability to say no to Emu’s pleading face is starting to kick in. 

“I didn’t bring swim trunks,” he tries as a last ditch effort to get out of this, but Kiriya just shrugs his shoulders as though it’s a non-issue. 

“Just get naked then,” he says, and Hiiro’s cheeks flare bright red at the suggestion. 

“I will not,” he says sharply, but Emu rolls his eyes as if he’s being silly. 

“Come on, Hiiro-san, it’s not a big deal,” he says, and it stings a little, because of course it wouldn’t be a big deal to Emu. But over the past few months Hiiro has been growing closer to both him and Kiriya, and as much as he doesn’t want to admit it he’s started to see them both as... important. Which is ridiculous, because he knows that they’re together, and they have no reason to want him. 

Something in his face must give away his trepidation, because Kiriya makes a soft little clicking sound that Hiiro realizes is supposed to be comforting, and reaches out to squeeze his shoulder. 

“If you really don’t want to, you don’t have to,” he says, and it’s that little bit of genuine kindness and caring that pushes Hiiro over the edge. 

“...No, it’s fine,” he mumbles, his cheeks still red as he reluctantly pulls off his shirt. He can’t continue to fight after that, it just wasn’t fair. Emu seems pleased, at least, from the way that he waits eagerly by the edge of the pool for Hiiro to finish getting undressed. Hiiro stops when he gets down to his underwear, giving Emu a pointed look and then gesturing for him to turn around when the merman just continues to watch him. Emu huffs, but does as he’s told, and Kiriya laughs until Hiiro gestures for him to turn around too. He does so as well, making a big show of it, and Hiiro grumbles something impolite under his breath as he takes briefs off and folds them with the rest of his clothes. 

When he turns back around he sees that Emu is watching him again, and it looks like he’s... appreciating what he sees. Hiiro flushes and tries not to let it bother him too much as he heads over to the edge of the pool and sits down, letting his feet dangle into the water. He supposes the human body still must be a curiosity to these two, even though they themselves appear human more often than not. But it’s not like Hiiro hasn’t been interested in their bodies too, as strange and different as they were, so he tries not to read too much into it. 

Emu smiles at him once he starts to relax a bit, and Kiriya slides back into the water himself, watching Hiiro as he slowly lowers himself into the water with a little splash. He clings to the edge of the pool at first, trying not to panic at just how deep the water really is, and Emu quickly places his hands on his shoulders, squeezing reassuringly. 

“It’s ok, Hiiro-san. You can hold onto me,” he says, and Hiiro takes a deep breath and nods. Letting go of the wall is still a lot harder than he’d thought it would be, but he lets Emu take hold of his arm and slowly guide him further into the pool.

He can sort of feel the waves here, closer to the entrance where the pool leads out into the open sea. It’s unnerving, and he clings tightly to Emu’s arms as the merman guides him. 

“You’re alright, Hiiro, you’re doing good,” Kiriya says, his voice low and soothing as he follows behind them, and Hiiro can feel his tail brush against his legs every now and then. Normally he imagines the sensation would be terrifying, but right now it’s comforting, and Hiiro slowly lets out the breath he had been holding in. 

He moves his legs a little, just gently treading water the way he vaguely remembers it from back in school, and Emu smiles at him encouragingly. He doesn’t let go of his hands, just holds Hiiro in place as he starts to get the hang of it. He has to admit it’s nicer than he thought it would be, though he certainly wouldn’t be swimming on his own any time soon. Emu is close to him, their bodies almost touching, and for a second Hiiro wants to kiss him. But then he feels Kiriya’s tail bump against the back of his knees, and he immediately snaps out of it. He licks his lips, feeling a little ashamed of himself, and turns his head away. 

“Hiiro-san? Is it a little too much?” Emu asks, sounding concerned, and whether by accident or in some weird attempt to comfort him, his tail slides right in between Hiiro’s legs. 

It feels nice, the scales are smooth and cool against the skin of Hiiro’s thighs, and Hiiro is very, very glad that the water is cold enough to hide his slight arousal. He still jerks back, his face bright red as he bumps into Kiriya behind him. 

“Hiiro-san?” Emu squeaks, surprised, and Kiriya hums as he straightens him out. Hiiro suddenly feels even more naked now between them than when he had first taken his clothes off, and he swallows thickly before licking his lips again in an attempt to get his mouth working. 

Kiriya’s eyes trail down to watch the movement, and for a second Hiiro thinks his gaze is absolutely predatory. Then he mutters something that sounds like ‘oh screw it’ and tilts Hiiro’s head to the side and kisses him. 

For a second Hiiro doesn’t react because he’s shocked. He just stays absolutely still as Kiriya’s way-too-sharp teeth press against his mouth, and then an inhumanly long tongue pushes its way between his lips. Then Kiriya makes a questioning little trill as he tilts his head to the side, and Hiiro melts. He opens his mouth for Kiriya, letting his tongue in, and he finds himself grasping tightly to Emu’s hands for purchase, needing something to hold onto--

Emu makes a surprised little noise in his throat and Hiiro immediately pulls back from the kiss. He instantly feels terrible, kissing Emu’s boyfriend in front of him, while holding onto him. Even if Kiriya was the one to start it first, and that still seems like a dream of some kind, but it doesn’t excuse his actions at all, and right now he’s torn between apologizing and trying to disappear. 

“Kiriya,” Emu says, and he sounds tired and slightly chastising, and Hiiro is ready to apologize but Emu isn’t even looking at him. “We said we’d wait until Hiiro-san makes the first move.”

Hiiro pauses then, apology already half-way out of his mouth, and Kiriya grunts, his tail winding around Hiiro’s legs to twist together with Emu’s. 

“If we waited for Hiiro to make the first move we’d all be old men by the time anything happened,” Kiriya says, and Emu still looks a little annoyed, but he’s not mad, and more than anything Hiiro is confused. 

“You’re... not angry?” he asks, slowly, hesitantly, and Emu looks a bit surprised that he’d even ask the question. 

“Of course not,” Emu says, then pauses before a cheeky little smile comes to his face. “Or at least, I won’t be as long as you kiss me next,” he adds. Hiiro thinks his face must be giving a tomato a run for its money, and he squirms a little in the loose coils of Kiriya’s tail. 

“But, you--” he begins, and Kiriya sighs as he rubs his back.

“Emu and I like you, Hiiro,” he explains, and Hiiro’s mouth opens and closes like a fish. Emu takes that chance to get his own kiss like he said he would, leaning in and capturing Hiiro’s lips expertly. His kiss is softer than Kiriya’s, a little less dominating, but it’s still intense, and Hiiro soon finds himself leaning into it. His body feels hot even with the cold of the water around them, and once again Emu’s tail slides in between his legs, rubbing against him. Hiiro gasps at the feeling, and he feels as though he’s about to come apart as Kiriya presses up against his back as well. 

“Are you ok with that, Hiiro-san?” Emu asks as he pulls away and his lips are red and wet and Hiiro can’t help but swallow as he slowly nods.

“But aren’t you... together?” He asks anyways, because he still can’t quite wrap his mind around it. Kiriya and Emu share a slightly confused look before Kiriya seems to come to a realization. 

“We’re not monogamous, Hiiro,” he says, nipping at Hiiro’s neck just enough to leave a slight impression of teeth. “Emu and I are partners, but we both take other partners too. It’s pretty rare that we’re both interested in the same one, but...” 

He trails off, and Emu leans in close, kissing at the mark that Kiriya just made. 

“But we decided to make an exception for you,” he says, and Hiiro feels like he’s melting again.


	5. Chapter 5

**Summary for the Chapter:**

> This chapter is just porn so if that's not your thing, you can skip it.

They get out of the water shortly after that, Hiiro shivering slightly as Emu pulls him in closer and kisses him aggressively. He still has his tail, the edge of his fins dipped into the surf. Hiiro isn’t sure what he had expected this night to be like, but this is definitely better. 

“Hiiro-san,” Emu says, his voice quiet and breathless as he leans in close to Hiiro’s ear. “I want to have sex. Is that ok?” 

Hiiro freezes then, going still, because that had definitely not been what he was expecting to hear. He isn’t sure if it’s ok, really, because he’s never had sex with anyone before, and while he is very, very attracted to Emu, he isn’t sure if he can actually do that right here, right now. His palms start to sweat and he licks his lips, trying desperately to wet his mouth so that he can come up with some kind of response, but luckily Kiriya notices his distress and pulls himself out of the water. 

“It doesn’t have to be tonight,” he says, and Emu looks a bit sheepish as he nods his head. Clearly he had been hoping for tonight, but he too notices that Hiiro looks less than enthused, and he places a hand over top of his and squeezes. Some of the pressure leaves Hiiro then, and he exhales in one long breath. 

“I’ve never… done that before,” Hiiro admits quietly, and Emu blinks before he and Kiriya share one of those communicative looks between the two of them. 

“It’s ok, we can take care of you,” Kiriya purrs, wrapping his arms around Hiiro’s torso. 

“Whenever you’re ready,” Emu adds quickly before Hiiro can tense up again. 

Hiiro nods, trying his best to relax his muscles as Kiriya slips back into the water for a second before climbing out, his legs having made a reappearance. 

“Anyways, it’s getting late, so we should be getting back soon,” he says, changing the subject. Hiiro is grateful for it, even if he’s sad when Emu disappears into the water to change back himself, already missing the warmth of him. 

*** 

Kiriya and Emu never push the issue of sex again. The invitation is there, clearly, in the way that they sometimes look at him, but they’re very careful not to pressure Hiiro or push him into something he doesn’t want to do. Hiiro appreciates it, he really does, but therein lies the problem. 

He does want to do it. He really, really does, and he wants to more the deeper he falls into this relationship, the more time he spends with the two of them. Their trips out at night are the same as they’ve always been, except with more kissing, but everything about them feels more intimate now, more meaningful, and Hiiro still can’t believe that these two amazing people actually want him. But it becomes clearer and clearer the longer that they’re together, and Hiiro finds himself wanting. 

He has no idea how to broach the subject, though, his own inexperience making him feel embarrassed and childish. 

More than that, though, is the fact that the time seems to have flown by, and soon, Hiiro is realizing that the term of his position is almost up. He only has a month left as the head of medical staff on the island, and then he’ll be heading back to Tokyo. 

He doesn’t bring it up to Kiriya and Emu. The truth is he wants to extend his term, so that they can spend more time together, but when he brought it up to Genm they told him that they’d already found a replacement for him. It’s scary, leaving when he finally has a real relationship for the first time since Saki died, and maybe even before then.

Neither Kiriya nor Emu bring it up either, and Hiiro knows that they know - his term had never been a secret and Asuna had brought it up on many occasions – but he thinks that they might be as scared as he is. And that’s a ridiculous thought, because neither Kiriya or Emu had ever seemed afraid of anything, with the exception of that one time a cockroach got into Kiriya’s bedroom while they were making out. But this is nothing like that, and Hiiro doesn’t know how to face it. 

So, in his usual fashion, he doesn’t face it, up until less than a week before his departure. 

He isn’t even sure what set him off. Maybe it was Asuna earlier that day, asking him if he’d finished packing yet. Maybe it was his father’s phone call letting him know how much he missed him, and that he’d be waiting at the airport when he got off his flight. 

Either way, when he goes to the cave with Kiriya and Emu for the last time, he brings a blanket with him. Neither of the other two ask him what it’s for, and neither of them seem surprised when he asks them to wait instead of swimming off right away. 

“I want to...” He begins, then pauses to lick his lips. He isn’t sure what the right order for this is, or even how to say it, but when he looks up and sees Emu looking at him expectantly he ends up blurting out everything on his mind without even thinking. “I think I love you. The both of you. And before I go, I want to… I want to have sex, so I can remember you.” 

His face is burning by the time he finishes, and Emu looks both happy and a little sad, but Kiriya just looks overwhelmingly fond. 

“It’s not like we’re never going to see each other again, dummy,” Kiriya says softly as he crawls up into the edge of the pool and wraps his arms around Hiiro. Emu nods his head and quickly joins the hug, and Hiiro feels all his muscles relax at once as he nods his own head, trying his best to keep himself from crying. He’s never cried in front of anyone before, not even at Saki’s funeral, and he doesn’t want to start now. 

But at the same time he can’t help it, because he loves these two men so much, and he has the feeling that they feel the same way about him. 

He’s happy that he already laid the blanket down over the floor of the cave as Kiriya pushes him down, kissing him deeply while Emu undoes his belt and pants. Hiiro touches him reverently, running his fingers first over his pecs and then down to his abs, and Kiriya smiles into his mouth as Hiiro’s hands hesitate, then slide down to where his torso meets tail. It’s not the first time he’s ever touched him there, but it’s the first time he’d done it in a romantic way, and Hiiro loves the way that Kiriya gasps a little into his mouth as he slides his fingers along the seam of his gills, then underneath the tiny little fins by his waist. 

Emu takes advantage of Hiiro’s distraction to divest him of his pants, and soon Hiiro is the one gasping as Emu wraps his hand around his cock, gentle and slick with who knew what, but it was warm, and it makes Hiiro feel all tingly deep in his stomach. 

Kiriya grins as he reaches up with one hand and flicks at Hiiro’s nipple, causing him to gasp and arch his back, and Emu smiles slyly as he pinches the other one, his other hand still on Hiiro’s cock. Hiiro loses track of his hands for a minute, and all he can do is feel, but then Emu grabs his hand and moves it down to his own tail, to a slit in the front that is wet and slick and needy. 

“I want you inside me, Hiiro-san,” he whispers into Hiiro’s ear, and a shiver goes down Hiiro’s spine, because he had never anticipated that. He had always expected that he would be the one receiving, but   
for Emu to say that he wanted him, wanted him in that way… But Kiriya quickly shakes his head. 

“No, that’s not a good idea,” he says, though Hiiro doesn’t understand why, and Emu seems to pout a little bit. “His isn’t flexible enough, it’ll just end up hurting a lot.”

Hiiro raises his eyebrows, and Emu’s hand on his cock stills for a second. 

“You have experience with this?” Hiiro asks, and Emu looks just as interested in the answer. Kiriya just grins and shrugs, and that in itself is answer enough. It is helpful, though, because Hiiro doesn’t know what he’s doing, and he doesn’t think that Emu is used to having a human partner either. The idea of being instructed too does funny things to Hiiro’s stomach, and he swallows, his dick jumping a little bit as he asks, quietly, “So what should I do?” 

Kiriya eyes him for a minute, taking in his hooded eyes and the flush on his cheeks, and then his grin turns predatory as he leans in and kisses him again. 

“Use your fingers,” he says, and Emu gasps as Hiiro does as he’s told, sliding his finger against the slit. “Play along the outside, get your fingers nice and wet and then push one in, slowly.” 

Hiiro does, and Emu squirms a little bit at the sensation. Hiiro himself doesn’t know how to describe it; inside of Emu is warm and wet and welcoming, but it’s also tight, and soon he can feel something solid and flexible pushing at his finger, forcing it out. Soon the object pushes its way out of the slit as well, a lighter pink than Emu’s scales, and wiggling with a mind of its own almost like a tentacle. Hiiro stares at it, transfixed, until Kiriya leans in and whispers in his ear again. 

“Now you can use that pretty mouth of yours. Get down there and suck it,” he says, before turning to Emu with a conspiratorial look on his face. “You’re gonna love this, Emu, trust me.” 

Hiiro does as he’s told like a good boy, watching confusion blossom on Emu’s face as he crawls over until his newly-freed cock is right in front of Hiiro’s mouth. He can feel saliva gathering beneath his tongue just at the sight and smell of it, salty and musky in a way that Hiiro never knew could drive him crazy. Emu doesn’t seem to know what’s about to happen, though his dick slides against Hiiro’s cheek, pressing into his face as though saying hello. Hiiro inhales deeply, then pulls back just enough to open his mouth and take the slim, tapered tip of Emu’s dick between his lips. 

Emu lets out a startled noise, followed by a long moan as Hiiro takes more and more into his mouth, listening to Kiriya give a litany of instruction on how much to take at a time, how to suck and use his tongue. Hiiro is a fast learner – he has always had an affinity for lollipops – and soon Emu is writhing underneath him, his hands coming up to tangle in Hiiro’s hair and pull him a little bit closer. Kiriya’s hands take that opportunity to go elsewhere, a slick finger sliding in between his cheeks to poke at his entrance. 

Hiiro makes a needy noise at the feeling, that same slick making his skin feel hot and needy, both inside of his mouth and around his ass, and he wiggles his hips a little bit to get Kiriya to go faster. Kiriya laughs at him, then holds him still, sliding one finger in slowly up to the first knuckle. 

It gets very difficult for Hiiro to focus on the blow-job he’s giving to Emu as Kiriya slowly fingers his ass, stretching him out and getting him ready. But he keeps instructing him the whole time, telling him what to do and then warning that if he doesn’t please Emu properly, he won’t get fucked the way he wants. That is enough to get Hiiro’s concentration back on board, and Emu is moaning out a litany of ‘yes, good’ and ‘right there, Hiiro-san!’. Eventually Kiriya tells him to use his fingers again, sliding them in right underneath Emu’s cock, feeling the warm tunnel of before but so much tighter, sucking him in. 

Emu practically howls at that, thrusting into Hiiro’s mouth and onto his fingers, and soon Kiriya’s fingers are gone, replaced by the slim tip of his own slick cock working its way into Hiiro’s hole. It makes fireworks go off behind Hiiro’s eyes, and he moans needily around Emu’s cock as Kiriiya works in inch by inch, the whole thing squirming and moving inside of him until it’s all inside. Hiiro has no idea how big it is, or how it would compare to a human’s cock, but it feels enormous, filling him up so perfectly. For a second he forgets how to breathe or how to suck, before Kiriya is reaching around and tweaking his nipples, making him (embarrassingly) come first. 

“We’re not done with you yet, Hiiro,” Kiriya says when he notices, and he thrusts in, nice and slow, and Hiiro whines because he’s entirely too sensitive. He feels like his entire body is on fire, and soon Emu is coming into his mouth, down his throat, his hands going lax in Hiiro’s hair. Kiriya is still thrusting as Emu pulls out, and a bit of come mixed with drool dribbles out of Hiiro’s mouth. 

“That’s it, you’re doing so well, good boy, Hiiro-san,” Emu says as he starts stroking his hair, and Hiiro groans, his dick starting to twitch again as Kiriya finally, finally comes inside of him. Emu leans down and kisses him as Kiriya pulls out, making Hiiro whimper. Kiriya kisses his neck, sinking his teeth in just enough to leave a mark. Hiiro whines at the pain-pleasure of it, his entire body feeling far too sensitive, but then Emu goes to the other side of Hiiro’s neck and bites him as well just as Kiriya takes his own kiss. 

“You’re ours, Hiiro,” Kiriya says against his lips, and Hiiro uses the last bit of energy he has to nod his head before he goes limp, falling back against the blanket. Emu and Kiriya lay beside him, wrapping their arms around him and cuddling in close, and Hiiro snuggles into both of them. 

“Yours,” he mumbles, just as he starts to fall asleep.

**Notes for the Chapter:**

> There will be one more chapter after this, if all goes to plan. Sorry for the long wait for this! Life has just been hectic.


	6. Epilogue

For the first six months after Hiiro leaves on the ferry, Emu writes him regularly. His letters are usually long and rambling, talking about how things have been going with the other doctors and some of the researchers who Hiiro never bothered to learn the names of. Kiriya sometimes adds in notes and additions here and there, occasionally doodling on the back of the page (and always signing his name when he does). Hiiro writes back, as much as he can considering how busy he is going back to his old position as the head cardiac surgeon at Seito University Hospital. 

And then the letters abruptly stop coming. 

Hiiro thinks it’s just a matter of time at first, that Emu is just busy and hasn’t had a chance to write for a while. But after three months of radio silence, that excuse falls flat, and Hiiro starts to worry. He sends his own letters, which get returned by the mailing service within a few weeks. When he mentions it offhand to his father during their weekly brunch, he nods his head as though that makes perfect sense. 

“Well, Genm did end up tanking that facility not long ago,” Haima says as he takes a bite of his omelet, and Hiiro’s fork stops half-way to his mouth. 

“What?” He says, rather dumbly, and Haima just shrugs his shoulders as he continues his meal. 

“Yes, all the employees were laid off without warning. I don’t know why, they never released a public reason.” 

Hiiro’s mouth feels abnormally dry, and he reaches for his glass of water, but his hand is shaking a little and he almost spills it instead. His father gives him a concerned look, and Hiiro quickly shakes his head, forcing himself to calm down. 

He had never gotten any contact information from Emu or Kiriya besides their mailing address at the facility. Personal cell phones hadn’t been allowed on the premises, so Hiiro had never gotten a number from either of them. They have his address, of course, but the lack of contact is alarming. 

Hiiro worries for another three months straight, to the point where it starts affecting his health. His father demands he go on stress leave, and for a while he considers going back to the island, just to see if by any chance Emu and Kiriya are still there. It’s still private property, though, even if the research facility has been abandoned, and Hiiro doesn’t want to risk being charged with trespassing. 

So he waits, instead. He spends most of his time at home waiting for a letter that never comes, and after a month of stress leave he finds himself growing numb to it. 

He goes back to work. 

More months grow by, and eventually he stops expecting a letter. He still waits, still worries, but deep down he knows that further correspondence isn’t coming. He just hopes it’s because Hiiro and Emu simply got tired of him, as much as the thought hurts, and that nothing has happened to either of them. 

Eventually, the years pass, and he stops waiting. 

He goes on a few dates, here and there, usually with men from the hospital. Coming out to his father is the hardest thing he’d ever done in his life, but he does it, since there’s no point in hiding it anymore. But none of the relationships ever stick for more than a week or two, and in a way it makes Hiiro angry.

That doesn’t last particularly long, though. 

Anger takes effort, after all, and Hiiro doesn’t have the energy lately to stay angry. Mostly he just feels a dull, numb pain, and he wonders how long it will take before that goes away too. 

*** 

Six years after his position at the research facility ended, Hiiro’s life is boring but successful. He’s one of the best doctors in the world, just like he’d promised Saki. Everything is exactly the way it should be, and the year he spent on that island is nothing more than a distant dream. 

Until one day, when one of his nurses comes up to him in the hallway and grabs him by the sleeve to get his attention. 

“Kagami-sensei? The new coroner was looking for you,” she says, and Hiiro raises his eyebrows. 

“Why?” He asks, curious, because he rarely has business with that department, but the nurse just shrugs her shoulders. 

“He didn’t say, he just asked to send you down to the morgue if I see you,” she says, and then, message delivered, she’s on her way. Hiiro supposes it’s a good thing, that the nurses and other staff no longer see him as a celebrity and are able to approach him so casually, but he’s also curious. 

He heads down to the morgue on his lunch break. 

He knocks on the door to the office as he arrives, and hears the sound of somebody moving around before a somewhat familiar voice calls ‘come in!’. He isn’t quite sure where he knows it from, though. 

The coroner has his back to him when he comes in, checking something on a chart on the wall, and Hiiro raises his eyebrow as he steps in and clears his throat. 

“This is Kagami, you needed me for some--” He breaks off as the coroner turns around, and something inside of his chest squeezes tight. 

Kiriya is standing in front of him, looking older but also very much the same as he had the last time that he’d seen him. There’s wrinkles around his eyes that were never there before, Hiiro thinks, but he can’t quite remember well enough to know for sure. 

He stares for a long minute, unable to say anything, and Kiriya stays quiet in return, giving him a moment to process things. In that moment, Emu comes through the door, wearing a doctor’s coat and a nametag that says ‘Houjou, Pediatrics’ clipped to his front pocket. 

“Kiriya, I can’t find him any—oh. Hiiro...-san,” Emu says, breaking off when he sees Hiiro standing there. Hiiro stares at him too, wondering if this is real or if he’s in some kind of weird fever dream. 

Emu shifts from foot to foot awkwardly under Hiiro’s scrutiny, and soon Hiiro jumps when he feels Kiriya’s arm around his shoulders, just a bit stiffer than he remembers it being before. 

“You’re freaking him out, Kagami,” he says, and Hiiro doesn’t miss the use of his last name. He flinches a little at it, and Emu quickly shuts the door to the office so that they won’t be disturbed. Hiiro shrugs Kiriya’s arm off of his shoulders, and makes a point not to look at his expression as he does so. 

“What do you want?” Hiiro asks, and it comes out a bit more bitter than he had really intended. But honestly, he is bitter, and he can’t keep it out of his face or his voice. Emu looks a little hurt by it, and for a minute it makes Hiiro feel better, but then it only makes him feel worse. He can feel Kiriya’s eyes on his back, but he still doesn’t want to turn around and look at him, so instead he focuses on Emu’s shoes. 

“We came as soon as we could,” Emu says, softly, and Hiiro snorts, because really, the soonest they could come was six years? 

Kiriya reaches out for him again, just a simple hand on his shoulder this time, and Hiiro doesn’t have the energy to shrug him off. In fact he doesn’t have the energy to do anything, except look down at Emu’s feet.

“If you’ll let us explain,” Kiriya begins, but Hiiro frowns and he trails off with a sigh. Except Hiiro isn’t frowning at Kiriya, he’s frowning at Emu. There’s something different about his foot, the right one, and it catches Hiiro’s attention just long enough to make him curious before he realizes what it is. 

His eyes widen and he crouches down, reaching for Emu’s pantleg, and Emu squeaks at the sudden movement, but then his face turns red and he turns his eyes away, shoving his hands into his pockets. 

“We got found out,” Emu explains as Hiiro examines the prosthetic replacing the majority of his foot. It’s well made, replacing everything from the heel down. Hiiro’s breath comes in sharp as he looks it over, and Kiriya crouches down next to him, hand on his shoulder again. 

“Emu lost it when we escaped. We had to lie low for a while, we couldn’t risk coming back to Japan or contacting you. Hiiro, I’m sorry,” Kiriya says, and he sounds genuine. Hiiro bites his lower lip as he gently places his hand on Emu’s ankle, then what’s left of his heel. 

“Can you still swim?” He asks quietly, and Emu’s face softens as he crouches down so that they’re all on the same level. 

“It’s a little harder, now. I wanted to find someone who could make a prosthetic for that too, but, you know, that’s a bit tough.” He cracks a smile, and Hiiro can’t find it in him to smile back. 

“...I thought you got tired of me,” he says, his voice far smaller than it is normally, and Kiriya shifts, his arm wrapping around Hiiro’s shoulders in a tight hug as Emu comes in and embraces him from the front. 

“Hiiro, we would never get tired of you,” Kiriya says gently, and Hiiro is so, so happy to hear his first name from him again. He bites his lip and blinks back the tears that he knows are gathering, because he doesn’t cry in front of other people. But it’s hard not to when the two people he’s been waiting for for so long are finally with him again, 

Emu brushes his hair back behind his ear and kisses him, all softness, and Hiiro hesitates for a moment before he slowly returns it, wrapping his arms around Emu tightly and holding onto him as though he might disappear. 

“We’re not going anywhere anymore, Hiiro-san,” Emu says, holding him just as tight, and Kiriya leans in to kiss Hiiro on the cheek. 

“We’re here for good this time. You’ll never be able to get rid of us again.”

**Notes for the Chapter:**

> And here we go, another story finished. This one took a bit longer. I'm not really sure how happy I am with the epilogue because it kind of feels rushed to me, but I hope you all enjoyed this au!

**Author's Note:**

> Something that popped into my head after somebody on tumblr mentioned an ex aid merman au. I'm not even going to guess how long this one is going to be though, lol, but I'm hoping to have it finished before I got back to school in two months. Here's hoping!


End file.
